I've got several RFID access cards for various locations and I'd like to consolidate into one card or device. Can I use an app like NFC tools Pro to get it done on my phone or use some other methods to consolidate everything?

In on this thread. Wondering that too.

I would guess this could almost certainly do it.

https://flipperzero.one/

Depending on the cards and location you could ask if they could just program your access to use one of the existing fobs on all of them.  I've got one I use for quite a few places but I have admin rights to the software.

Be careful, your phone probably does not have the frequency receiver for your access card, Phones usually support certain RFID frequencies.

Also would you be authorized to do this? Technically I can use my Flipper Zero to clone some of the door access cards I have, but doing so and using the Flipper would get me fired.

Do you have one that's "yours", like the most unlikely one to be taken back?
And does it beep when you scan it on a reader?

Might talk to your security/IT/access guys and see if they can add "your" card to the access group instead of issuing you one.

I had a shitpile of them for radio sites, years ago I ended up consolidating to "mine".  
Now I roll up to the site, scan "my" badge, radio ops crew and have them add it to the ACL.  
Upside, one card opens a shitload of sites/buildings/gates/etc.  
Downside, don't lose that card.  I'd strongly recommend keeping a spreadsheet with what it opens and a contact in case that card gets lost.

Use a tool like NXP's TagInfo (android) to see if your phone can even read the badge.

Flipper Zero is the device I use for things like that. Also use it for some other tasks such as i-button via Dallas 1-wire but that's for other purposes.

How do you clone a key card with Flipper?  Can use set it in a "listen" mode and record a card within it's proximity?  I used to manage a gate system for a non-profit, and thought it would be nice to have a device which could recreate several codes vs carrying several cars for test purposes.